Originally Posted by
Simpleman
if you are aware of, and can pull off mastery snapshotting, then Stormsingers Fulmination Charge from eye of azshara is BiS - although from what level would depend. same level as youir current trinkets it is better (extra so if you can get ahold of the emerald Dreamcatcher legendary helm). also, the unstable Arcanocrystal from withered jim, the world boss of the last 2 weeks is BiS for both single target and AoE. Other good options include a good ilvl Devilsaur Shock Baton, the Naraxus' Spiked Tongue and the Swargming Plaguehive from nythendra.
to see which trinkets are better through different ilvls, i reckomend simming the different combinations of trinkets you have available to you, as the variation in them and their level makes it rather hard to predict and guess which one will be better.
NB: Another thing to note is the range that you are from the boss for Naraxus' Spiked Tongue. Depending on your tactic, in phase 3 of Xavius the raid generally stacks up on the boss, so you cannot keep the 20 yard range, and so the value of that trinket drops off in arguably the most important part of the fight when you are DPS race against time of getting mind controlled.